This invention pertains generally to amplifiers and more particularly to amplifiers with compensation circuitry for reducing variations in an output signal of the amplifier due to the effects of temperature variation and signal level variation.
As is known in the art, amplifiers are used to amplify a low level signal to an appropriate higher level signal. For example, in an oscillator having a feedback loop with a feedback signal, an amplifier is used to amplify the feedback signal to offset attenuation of the feedback signal in the feedback loop. An amplifier is also used to amplify a signal from an oscillator to an appropriate level to provide a local oscillator signal to a mixer or to provide a strong signal from a weak signal as necessary. A typical requirement for a gain compensated amplifier is to provide a signal with a constant signal level at the output of the amplifier while in operation. In a changing environment wherein the amplifier is exposed to changing temperature which changes the characteristics of the amplifier, the level of the output signal of the amplifier will typically vary. Also, input signals will vary in level due to changing characteristics of the circuitry which provides the input signal. Thus it is not uncommon for the signal level of the output signal of the amplifier to vary. In an application wherein the amplifier must provide a signal with a constant output power signal level, it is desirable to minimize variation in the level of the output signal of the amplifier.